I haven't gotten around to messing with this yet this week, but I've been looking at the service manual and diagrams and came up with the following:

My Symptoms:

-Running warmer than normal, but not overheating at highway speeds. (Can't hear fan)
-Climbs toward overheating at low speed/idle and boils. (Can't make out fan with engine running).
-Temp decreases to same as highway speed when able to run highway speed again.

After looking at the location of the temp sensor and fan switch, I'm leaning heavily toward the thermostat. My theory is that the coolant in the radiator (just before it exits, and where the switch is located) may be getting low enough to turn the fan off, but the temp at the thermostat, where it's coming in is getting too hot, but the thermostat is opening or stuck open enough to allow flow to cool (but not completely) when moving.

I'm in the process of pricing a fan switch, thermostat and new radiator cap. If I can swing all 3, I'm going to do it. I'd rather replace parts so that I know what is new and (hopefully) good that way I have more things I can eliminate in the event of future problems.

Thoughts?

 

I dont know if this will help you but, I have a 93 1000f and it to runs hot in city driving. The temp gauge gets to about 3/4 and then the fan kicks on and cools it to 1/2 and then turns off. I can hear the fan went it turns on, even with the motor running and sitting in traffic. I was told that they run hot in traffic and city driving. There are some other postings here on this forum that talk about what you can do to help keep the bike cool.

1. was to run a main switch to the fan so you can turn it on, before the bike gets too hot.
2. was to replace the stock termostat with a honda car termostat (they are bigger and let more coolant flow at a lower temp.)
3. when you replace your coolant, use some stuff called "water wetter".

Those are just somethings that i have read, that sounds like they might help with keeping the temp down. Good luck and fixing the problem.

 

Just to update for anybody who searches on this thread: New t-stat and O-ring fixed it.

 

so how is the bike running now? now that you have the ring and therm-o changed it should be sitting around 1/4 and in the city just below half.

 

Im having the same issue. I changed the Coolant, Thermo Sensor, and put power to the fan and they are fine. Next stop seems to be Thermostat. Mine differs slightly in that the temperature gauge needle actually goes past the red and onto the stop.

 

When dealing with temp issues like this, don't underestimate the importance of the radiator cap. It's a pressure relief valve that holds pressure on the system of 13PSI, effectively raising the boiling point of the coolant. (Remember your science classes?) If the pressure is not maintained the coolant can boil at idle when temperatures are elevated but still not beyond the design paramaters.

Radiator caps can be purchased at the auto parts store by matching them up with a common cap from many '90's Mitsubishi cars. Unfortunately I don't recall the model number but if it looks right, is rated at 13PSI, and is listed as used on many of those years Mitsubishi, that's it. Expect about $7 that way vs: $25 or so from the bike dealer.

 

+2 on the radiator cap. I didn't have any problems with mine, but I'm going to replace it soon since they're cheap and mine's old anyway.

My bike is now running as you said, in the lower 1/4 at highway speeds (even on the 98+ dayswe've been having lately) and 1/2 to 3/4 in the city on the hottest days. I'm pleased with how cool it's staying now. I rode it for over 4 hours on Sunday and not one issue. Man, I love this bike. If it weren't so uncomfrortable. I'm getting more comfortable leaning now. I was actually dragging the toes of my boots the last time I was out. Time to start learning to counter-lean moreI guess.

 

I just "flushed" my system, I say flushed in quotes cause there was about 1/2 of what should have been in there.

Turns out, the overfill hose to my overfill tank was split RIGHT at the radiator cap, thus causing the coolant to bust out only when under high temp, leaking all my coolant. I cut off about 1" and put it back on. Temps are in the lower half now.

Hope this helps!

 

I have had the cooling issue as well, and I changed all the radiator hoses because they were all old and about to go. In addition to that my '93 1KF waas spitting out radiator fluid at red lights, you may have to check the level in the whole system. Good Luck!

 

While we're on the topic, another cooling system component worth looking at is the three way fitting that appears in the top corner of the right fairing opening, just below the thermostat/cap housing. From the side it may only appear to be a connector but there's a third hose coming in from behind. The finish on it may appear to be a die cast aluminum part but it is in fact a fiber reinforced plastic. Over time they start to deteriorate from the inside, get mushy, and start to collapse. Small leak at first that may appear to be the hose loose, which it in fact is, because the thing starts to collapse. Tighten it, think it's fixed, and it shows up again but worse. That is the description of how I found out about this on mine. It was about 10 years old at the time and was reading about 70,000 miles.